I used to be here under a different name, and yeah, you're right, this place would have been crazy a week after the release of a new book before.
I'm not sure what happened exactly, but I think the time between Skin Game and Peace Talks made the story lose a lot of readers, and the wait for Twelve Months didn't help. Plus, well, I personally know a dozen people who left the series because of what happened to Murphy in Battle Ground, so I imagine you can translate that into a bigger number in the community.
The new fans that joined the series in the period since Battle Ground are mostly in Reddit, and that community (IMO) has a whole different vibe (as do most of the new fans). And, since JB was looking for new beta readers, I imagine a lot of the "old guard" are unable to help these days, which is a shame, I thought there were things in the book that didn't exactly fit and they would have caught maybe.
The reality is that it's been 10 years since the series had any real momentum, and a lot changes in that kind of time. Heck, I think even Jim's goal with the story is changing.